1. Field of the Invention
The present invention is related generally to a method for controlling and supervising etching processes effected by ions, radicals and/or neutral particles activated in a plasma by identifying an etching rate and an end point of a layer to be etched that is situated on a substrate during material erosion. The etching processes are particularly used in structuring or configuring electrically conductive thin films to which has been applied a photoresist mask. An evacuated recipient in the form of an evacuatable airlock chamber is used as an etching reactor, and a moveable holder for carrying the substrate is provided.
2. Description of the Related Art
The designational and dimensionally true structuring of thin films by etching processes effected by plasma-activated ions, radicals and/or neutral particles (referred to as dry etching) is a critical process step in the manufacture of VLSI semiconductor components. For instance see the book, VLSI-technology by S. M. Sze, McGraw-Hill, Int. Book Comp. (1984), and in particular the chapter "Dry Etching", particularly pages 305, 306 and 307.
In what is known as dry etching processes, a structured layer of photoresist is first situated on a layer to be shaped or on a substrate to be shaped. The problem, then, is that the structure of the photoresist is to be transferred dimensionally true onto the layer or substrate lying therebeneath. For example, the substrate can be of single-crystal silicon. To this end, the layer or substrate which has been locally coated with a photoresist is bombarded with suitable ions or is introduced into a plasma. The particles consisting of ions and neutrals that are chemically activated in the plasma react with the exposed layer or substrate material upon formation of a volatile compound so that local material erosion insues. The local material erosion may be promoted by a simple impact process using atoms, ions, or molecules (known as atomizing or sputtering).
Care must be exercised in developing etching processes to ensure that the reactivity of the plasma is such that the erosion rate for the photoresist and/or for the material under the layer to be shaped is optimally low, which can be accomplished by a suitable selection of initial gases. This requires that a separate etching process be developed for every layer material and also that material of the preceding and superceding layers be taken into consideration. Furthermore, since an extremely high reproducability is required for very slight dimensional tolerances of, for example, .+-.0.1 .mu.m the process must be constantly supervised.